Regulation effects of exogenous phenolic acids on allelopathy of a wild rice (Oryza longistaminata) accession of S37.

Four kinds of exogenous phenolic acids,including salicylic acid,fumalic acid,p-coumaric acid and p-hydroxybenzonic acid,were used to investigate their regulatory effect on allelopathy of the wild rice (Oryza longistaminata) S37. The results showed that though low in weed-suppressive activity,the four kinds of exogenous phenolic acids induced the enhancement of the allelopathic potential of the wild rice S37 in target weed plants,and the inducible effects were dependent on the kinds of exogenous phenolic acids,concentration and treatment time. After foliar spraying the exogenous phenolic acids,the inhibitory effects of the wild rice S37 on plant height,root length and fresh weight of Echinochloa crus-galli were significantly higher than that of the control. Especially at the concentration of 100 mg/L,the plant height and fresh weight inhibition rates of fumalic acid were 38.12 and 26.31 percent points higher than that of the control,showing fumalic acid was more effective compared with other phenolic acids for weed control. Furthermore,the weed-suppressive activity of aqueous extracts from wild rice S37 leaves was increased after treatment with exogenous phenolic acids and peaked at 48 h after treatment,and then gradually declined.